ISSUES, REQUIREMENTS AND CHALLENGES IN SELECTING AND SPECIFYING A STANDARDIZED ET EQUATION
|
|
- Arlene Bradford
- 5 years ago
- Views:
Transcription
1 ISSUES, REQUIREMENTS AND CHALLENGES IN SELECTING AND SPECIFYING A STANDARDIZED ET EQUATION R.G. Allen, I.A.Walter, R.Elliott, B. Mecham, M.E. Jensen, D. Itenfisu, T.A. Howell, R. Snyder, P. Brown, S. Echings, T. Spofford, M. Hattendorf, R.H. Cuenca, J.L. Wright, D. Martin 1 Abstract The ASCE Evapotranspiration in Irrigation and Hydrology Committee in cooperation with the Water Management Committee of the Irrigation Association has defined and established a standardized reference evapotranspiration (ET) equation. The purpose of the equation and standardized calculation of parameters is to bring a commonality to the methodology of reference ET and to the basis used to determine crop coefficients for both agricultural and landscape use. Issues and requirements in the selection and definition of the standardized procedure are that the procedure be understandable, defensible, accepted by science/engineering communities, relatively simple, and use existing and historical data and technology. The primary challenge was to select one or more equations that would satisfy the selection criteria. There have been traditionally two types of reference crops (grass and alfalfa) and six major reference equation types (Kimberly Penman, CIMIS 2 Penman, FAO Penman, ASCE Penman-Monteith, FAO-56 Penman-Monteith and NRCS Penman-Monteith) have evolved over the past thirty years, each having large groups of followers and related crop coefficients. In addition, the reference crop is a living crop and therefore changes in its height, leaf area, stage of growth, age, variety, stomatal feedback, and irrigation frequency impact its ET rate. Other challenges include a myriad of procedures used to predict net radiation, vapor pressure deficit and other equation parameters. Hourly and daily computation are both in common usage, therefore, it is important that hourly calculations, when summed for 24 hours agree relatively closely with calculations made on daily time steps. Key Words Reference Evapotranspiration, standardization, crop coefficients, crop water requirements Introduction In May 1999 the Irrigation Association (IA) formally requested that the American Society of Civil Engineers (ASCE) Evapotranspiration in Irrigation and Hydrology Committee define and establish a benchmark reference evapotranspiration (ET) equation. The purpose of the equation and standardized calculation procedures is to bring a commonality to the methodology of reference ET data and to the basis used to determine crop coefficients for both agricultural and landscape use. The committee, in association with some IA members, has held extensive discussions on the issues and requirements for a standardized reference ET formula and some of the challenges and problems in making the specifications. In addition, the committee has undertaken an intensive intercomparison of commonly used methods at forty-nine locations across the U.S (Itenfisu et al., 2000). The primary issue is to select and specify a standardized equation(s) that serves the needs of a large group of users nationwide and that is compatible with current de facto standard equations and data sets, and that represents reality (i.e., measured ET from a reference crop) over the range of climates and regions within the nation. Other issues are whether one equation can span calculation timesteps ranging from less than one hour to one month with little modification and whether it can form a basis for computing crop coefficients from field measurements that allow the coefficients to be transferable, across the United States. Additional issues are whether a simplified equation is acceptable when the loss of accuracy is less than a few percent and whether 1 Members of the ASCE Task Committee on Standardization of Reference ET and/or the Water Management Committee of the Irrigation Association. 2 CIMIS refers to California Irrigation Management and Information Service
2 it is important for the national standardization to follow an international standardization introduced by FAO in One last challenge is to present a fairly robust, yet simple procedure for converting crop coefficients between reference types to facilitate transfer of coefficients to new locations. Issues and Requirements Following are some of the issues and requirements that were discussed by the ASCE Task Committee on Standardization of Reference Evapotranspiration: 1. The selected ET computation procedure and resulting equations should facilitate determining crop coefficients for both agricultural and landscape usage. Irrigation water management in urban areas is increasing in sophistication and information requirements. Substantial and widespread research is being conducted to quantify water requirements for various types of urban and residential land-covers. There is need for a reference ET basis that is easy to understand, visualize and apply using commonly available weather data and that is simplified for application by urban users who may lack a background in physical processes of energy balance and aerodynamic processes. The visualization requirement suggests the need to include a grass reference basis for use in urban applications where turfgrass is a primary component. It is desirable for landscape cover coefficients (K c ) to be transferable across a wide range of latitude and climate. Therefore, it is important that the adapted standardization be as accurate as possible over a wide range of climatic regions. 2. The selected ET computation procedure should apply to both tall (alfalfa) and short (grass) references. This issue and requirement narrows the number of equations that have direct application for both tall reference ET (ET r ) and short reference ET (ET o ) approximations. For reasons already stated, ET o has a long history of application in urban areas and for agriculture in much of the U.S. Alfalfa has a long history for agricultural application in the midwest and northwestern U.S. Families of crop coefficients have been developed for each reference type. Wide adoption of any standardization will require a method that is able to produce both ET o and ET r values that adequately represent each reference type. Other methods that are tailored specifically for either ET o or ET r can be converted to the other reference type by multiplying by a conversion factor. However, there is substantial uncertainty in the ratio of ET r /ET o to use for conversion and how the ratio changes with location, time of year and with climate (Wright et al., 2000). Therefore, this approach to producing a method that is applicable to both ET r and ET o prediction was not recommended. 3. There are several methods that have been applied to both tall (alfalfa) and short (grass) reference surfaces. The ASCE Penman-Monteith equation (ASCE PM), included within ASCE Manual 70, used algorithms for surface and aerodynamic resistance that were tailored to both grass and alfalfa references. These algorithms have had considerable review and application and are considered to produce relatively accurate estimates of ET o and ET r over a range of climates and locations. In addition, the PM equation includes parameterization of resistance components that have a physical basis. This facilitates changing these parameters to fit various surface conditions or characteristics or for tailoring the equation to better fit measured ET. This characteristic of the PM equation along with its didactic form increases its appeal. The 1982 Kimberly Penman equation (Wright, 1982) includes a variable wind function that was developed to improve prediction of ET r for the southern Idaho climate. The 1982 Kimberly Penman equation was demonstrated to have high predictive accuracy in other regions of the U.S. and worldwide in the analyses conducted for ASCE Manual 70. In 1996, Wright (1996) presented a variable wind function to use with the Kimberly Penman
3 equation for predicting ET o. This form of the 1982 Kimberly Penman with grass wind function is referred to as the 1996 Kimberly Penman. Unfortunately, the 1996 Kimberly Penman was not included in the 1999 analyses conducted by ASCE (Walter et al., 2000; Itenfisu et al., 2000). In a recent analysis at an independent site near Bushland, Texas, the 1996 Kimberly Penman performed equally as well as the recommended ASCE standardized reference ET o equation in predicting measured ET o (Wright et al., 2000). 4. The ET computation procedure and resulting equation should have commonality and appeal to a wide range of users of reference ET data. The intention of ASCE was to adapt and recommend a method or methods that have received widespread usage and testing. There was insufficient time or resources to launch a research study to develop or refine a new method. This would have required the assembly and analysis of a wide range of ET measurement data from locations in addition to those that have already been included in equation development (such as in ASCE Manual 70). Although ASCE was careful to not allow international standardization and practice unduly influence practice within the U.S., there was some consideration given to current usage and practice within the international community. This included the recent release of FAO Irrigation and Drainage Paper No. 56 which adapted the FAO-56 Penman-Monteith equation as the sole ET o reference method. The FAO-56 PM equation is a direct derivative of the ASCE PM equation. Therefore, all things being equal, there were some international grounds for adapting the ASCE PM equation as the standardized method. 5. The standardized method should be compatible with current de facto standard equations and data sets Similar to the explanation provided above, the ASCE PM equation and implementation in the proposed standardization of ET o closely resembles the FAO-56 PM equation. This is advantageous in providing for more seamless transfer of crop coefficients and other information developed in the U.S. that are based on reference ET. The FAO-24 publication and various publications by the University of California and California Department of Water Resources contain a large number of crop coefficients that are based on ET o. Therefore, it is important that the adopted standardization reproduce the ET o that formed the basis of the published K c information sufficiently close so that the large base of K c information can be utilized with the new standardization with little or no modification. This was a primary supposition of FAO-56. A family of alfalfa-based K c s developed by Wright (1982; Jensen et al., 1990) have received extensive use across the U.S. It is important to support the future usage of these K c s within a standardization framework. 6. The adapted equation or variations on the equation should span calculation timesteps ranging from less than one hour to one month. Electronic data logging weather stations are becoming the norm. These systems are typically programmed to produce hourly and 24-hour summaries. Computing ET on an hourly or shorter time step has advantages of improved accuracy in locations where large diurnal changes in wind speed and direction or cloudiness occur that are not typical of patterns at locations where daily ET methods have been developed. Once programmed into a computer or data logger, computation of hourly ET is relatively straightforward. Basically, the increase in effort is for quality control and assessment of much more information than required for daily summaries. Even though hourly data are widely available and applied, it is important for the selected method(s) to apply to daily or even monthly summaries from historical periods. This is important in water rights work, irrigation water management, hydraulic design and in computing hydrologic water balances for historical time periods.
4 7. The adapted equation should provide for development of crop coefficients based on field measurements that are transferable across the United States. Serious field measurement of ET represents an enormous investment in time and money. It is economically advantageous to leverage the past investments in quantifying ET demands for various agricultural and urban vegetation and landscapes at specific locations. Providing a reference ET basis that reproduces the reference basis and characterization of evaporative demand over a wide range of climate and latitude does this. 8. The adapted method should have a simplified and compact form (terms simplified and combined) that is traceable to a full form equation. It is important to reduce any intimidation factor in the standardized method. Where possible and without the loss of accuracy, simplifications should be made to the finalized equation to facilitate its coding and debugging in computer programs and to enhance the process of teaching, presenting, and explaining the method. The full, original form of the equation should be retained as background to assist in educating the user in the various physical processes that govern evapotranspiration. The full form should also be referred to for research applications or for derivation or refinement of the simplified, standardized forms in the future. Challenges The following are some of the challenges faced by the Task Committee (TC) in analyzing and implementing the various requirements summarized above: 1. There is a large array and diversity of ET methods that have been developed and applied over the history of the U.S. There is diversity in the specific type and form of ET equations applied in various states. These include: Modified Penman equations Forms of the Penman-Monteith equation Forms of the Blaney-Criddle equation Jensen-Haise equation Hargreaves equation Pan Evaporation (direct and using various pan coefficients) Thornthwaite equation Various radiation-based equations such as the Priestley-Taylor, Makkink, Turc, and FAO- 24 equations 2. Six primary reference equations have attained substantial adoption and usage over the past 30 years: 1982 Kimberly Penman (24-hour, alfalfa reference) CIMIS Penman (hourly, grass reference) FAO-24 Penman ASCE Penman-Monteith (hourly or 24-hour, alfalfa or grass reference) NRCS Penman-Monteith (24-hour grass reference) FAO Penman-Monteith (special case of the ASCE PM for hourly or 24-hour, grass reference) The NRCS and FAO Penman-Monteith methods are direct derivatives of the ASCE PM and vary primarily in how specific intermediate parameters are calculated. 3. Two different reference crops, alfalfa and clipped grass are used, with usage generally divided among western States.
5 4. There is presently no clear de facto standard equation in the U.S. Many users concur with ASCE manual 70 procedures for calculating reference ET, however the ASCE procedures discuss a wide range of equations. The Kimberly Penman equation and the ASCE Penman-Monteith (or FAO-PM) seem to have the widest application within the research and technical communities. The CIMIS Penman equation was developed for hourly application and has no direct counterpart or procedure for application with daily or even monthly data. 5. There is no clear set of supporting equations for calculating net radiation, soil heat flux, and vapor pressure deficit The three most widely used procedures for predicting net radiation from solar radiation measurements are the procedures by Wright (1982), by FAO-56 (essentially the procedure of Brunt (1932)), and the procedure of Dong et al., (1992) used by CIMIS. Associated with these methods, are basically three approaches for predicting short wave albedo: The procedure by Wright (1982) uses albedo that varies with time of year to reflect the effect of sun angle. It employs coefficients for predicting the net emissivity of the atmosphere and surface that also vary with time of year. The FAO-56 method uses a fixed albedo (0.23) and fixed coefficients for emissivity with the intention of more universal application around the world. The procedure of Dong uses a sun-angle based prediction of albedo that is applied hourly. The equation was integrated for daily application by Martin and Gilley (1993). Comparison of the three methods over all latitudes and seasons (R.G. Allen, 1997, unpublished analyses) has identified time periods or latitudes where the three methods for albedo agree and time periods and latitudes where they are significantly different. The time-based equation by Wright (1982) calculates values that are up to 0.08 (i.e., 25%) higher than estimates calculated using the method of Dong during spring, fall and winter for many latitudes. The fixed albedo (0.23) recommendation of FAO-56 predicts within 10% of Dong for all months for latitudes between -30 and +30 degrees and within 15% of Dong (i.e., +/ albedo) for growing periods at all latitudes for 24-hour timesteps. It is uncertain whether Dong represents the more accurate estimate for albedo. More research and testing is needed to evaluate all three techniques. There is uncertainty in computing net radiation and soil heat flux during nighttime. Prediction of cloudiness and its effect on prediction of net emissivity is uncertain. The is additional uncertainty concerning computing sky emissivity across a wide range of weather conditions and during winter months There is uncertainty as to the best means to predict soil heat flux (G). Allen and Wright (1997, unpublished analyses) and other members of the TC have shown that basing G for hourly periods as a function of R n provides good results for reference surfaces. Allen and Wright and Wright et al. (2000) show that for daily timesteps, the air temperature based method originally proposed by Wright (1982) may worsen the prediction of ET ref compared to using G=0 as proposed by FAO-56 for daily time steps. Two traditional procedures have been used to predict mean saturation vapor pressure (e s ) for a 24-hour period when only daily or monthly weather data are available: Apply the saturation vapor pressure function (e o (T)) to the mean air temperature (i.e, e s = e o (T mean ) ). Apply e o (T) to both daily maximum air temperature (T max ) and daily minimum air temperature (T min ) and average the two (i.e., e s = (e o (T max ) + e o (T min ))/2 ). ASCE Manual 70 demonstrated the advantage of averaging e o (T) from maximum and minimum air temperature, especially in arid climates. Allen et al. (1994) argued that any upward bias of this procedure helps to counteract daily predictions of ET that are based on daily averages of wind speed. 6. Even though the ASCE PM and Kimberly Penman methods have received relatively widespread usage across the U.S., neither equation has received widespread testing against
6 validated field measurements over a wide range of locations. Much of this is due to prohibitive costs for collecting and validating high quality ET measurement data and difficulty in making precise measurements. Based on analyses made to date, no equation exists that has demonstrated predictive accuracy that is within +/- 10% on a daily basis over a wide range in climates. Therefore, selection of the method for standardization had to be made based on other factors in addition to validation tests at a few locations. 7. Some state agencies use hourly computations for routine ET prediction and some use daily and monthly timesteps. Many ET equations developed for application to daily timesteps produce estimates of ET from hourly computations that do not agree with estimates made on daily time steps when summed over 24 hours. Many times this has to do with non-linearity and phase incongruency associated with averaging weather data over 24-hour periods and averaging crop responses to climate over 24-hour periods (e.g. stomatal conductance). This is complicated by the fact that many of the common equations, including the Kimberly Penman and ASCE PM equation were developed using 24-hour data and have been less precisely defined for hourly applications. A challenge is to select an equation that can be readily modified to be equally accurate at predicting ET for hourly (or shorter) timesteps and for 24-hour calculation time steps. 8. There is large diversity in sources of weather data, types of weather data, how data have been summarized, and environments associated with weather stations A full toolbox of standardized procedures is needed to provide means for processing available weather data for a location into usable information for the standardized equation. The toolbox must contain procedures for estimating missing data or for producing reference estimates using reduced parameters when data are missing. The toolbox must contain procedures for estimating ET o or ET r at locations that are data short, i.e., some parameters (solar radiation, air temperature, wind speed or humidity are not measured). Options include: Predict missing weather parameters based on other parameters or based on regional and/or long-term averages and then apply the full standardized equation Apply a reference ET equation that requires only the data available, for example, the Hargreaves equation where local calibration is done by comparing the reduced equation to the standardized equation at locations in the region having full data sets. The local environment and general aridity of the area surrounding a weather station (i.e., lack of transpiring vegetation) can impact readings of air temperature and humidity. Simple yet effective standardized procedures for adjusting for the effects of weather measurements from nonagricultural settings are needed, such as those proposed by Allen (1996) and by FAO-56 (Allen et al., 1998). There is need to recommend procedures for characterizing and improving the integrity of weather data used in making ET computations. 9. There is a need to simplify terms if the simplifications result in insignificant amounts of error. The challenge is in balancing minimization of error and simplification of the standardized methods. Parameters evaluated by ASCE for impacts of simplification include: Latent heat of vaporization (λ) varies as a weak function of air temperature and therefore varies slightly with time of day. Basing λ on average daily temperature typical of the growing season, for example 20 o C, produces a fixed value of λ=2.45 MJ/kg. This value does not deviate from actual values for λ by more than 2% even in winter time when mean air temperature is 0 o C. Air density (ρ) is a function of air pressure and virtual air temperature. Virtual air temperature is a weak function of the ratio of vapor pressure to air pressure. If the latter
7 ratio is held constant, ρ can be expressed as a function of air temperature and pressure only, with pressure incorporated into the pyschrometric constant, γ, in the PM equation. Full expressions for aerodynamic resistance (r a ) generally include complex expressions for characterizing the effects of stability on eddy transfer. For reference surfaces, however, sensible heat exchange is generally small relative to flux of vapor so that boundary layer stability is near neutral and therefore stability corrections can be ignored with little error, even for hourly computations (Allen et al., 1996). Surface resistance (r s ) is a strong function of stomatal resistance of individual leaves. It is well known that r s varies with environmental stresses such as air temperature, vapor pressure deficit and solar radiation so that the value for r s changes with time of day (Allen et al., 1996). Some of these functions are poorly defined for grass and alfalfa crops especially for daily timesteps. For purposes of computing ET r or ET o using hourly timesteps where the intent is to sum ET r or ET o over 24-hour time periods, the absolute accuracy for each hour is of less concern than the accuracy of the summed daily total. Therefore, r s for reference ET applications can generally be fixed over time for simplicity and consistency in application. In the standardization effort, unique, constant values for r s were assigned for daytime and for nighttime periods for both tall and short references. These values were different from the 24-hour values (Walter et al., 2000). 10. Historically, the reference surface is a living crop having variation in time and location for height, leaf area, leaf morphology, stage of growth, age, and irrigation and/or precipitation frequency. These characteristics vary due to time and location and due to varietal differences. They may even vary from year to year due to changes in weather and stomatal response (Howell et al., 2000; Wright et al., 2000). For purposes of establishing definitions for the reference surfaces that are consistent, constant and reproducible in regard to their impact on the reference ET estimate, the above characteristics need to be fixed in regard to height, leaf area, stomatal resistance, aerodynamic roughness, albedo, and underlying soil moisture. In the Penman-Monteith equation as applied to a defined, constant reference, this implies fixing aerodynamic roughness and zero plane displacement as well as the value for r s. In the Penman equation as applied to a defined, constant reference, this implies fixing the coefficients in the wind function. The penalty for fixing parameters is that the flexibility to vary parameters to fit observations is given up in exchange for consistency and reproducibility of the reference across locations and regions. A subtle advantage of fixing terms in a standardized definition and procedure is that it may discourage development of localized reference methods that are based on faulty or biased measurements of ET or weather data. Errors and biases in ET measurements are prevalent. This places pressure on the method selected for standardization to adequately represent the reference ET condition over a wide range of weather and climatic conditions. 11. There is uncertainty in the ratios for ET r /ET o to be used in converting families of crop coefficients between reference types. There is concern that ratios of ET r /ET o that are computed from the standardized equations may not reproduce ratios of ET r /ET o from field measurements. Reasons for this are the lack of feedback in the common weather data set, errors in prediction of net radiation and soil heat flux and deviation of the standardized reference definition from the field measurements at a location (Wright et al., 2000). 12. There is uncertainty in the application of ET r and ET o equations during wintertime for both dormant and non-dormant conditions. Uncertainties include characterization of: Net radiation due to impacts of daytime length, changes in albedo and low sun angle. Surface resistance of living reference crops that deviate from the definition due to low temperatures, senescence or dormancy.
8 13. There is some uncertainty in how to incorporate impacts of unique diurnal patterns for wind speed into 24-hour calculation timesteps. Summary and Conclusions The issues, requirements and challenges listed represent the considerations that have been made by ASCE in directing efforts and technical work for selecting and establishing standardized procedures to compute reference evapotranspiration. Some issues and challenges have been difficult to assess or solve. Many of the decisions made or solutions found are less than perfect due to the nature of the physical processes being modeled and the randomness of nature in space and time. Presently, the ASCE Penman-Monteith has been selected by ASCE as the basis for the standardization with most supporting parameters based on FAO-56. It is anticipated that this standardization effort will continue to evolve with time as new information and procedures become available. References Allen, R.G Assessing Integrity of Weather Data for use in Reference Evapotranspiration Estimation. J. Irrigation and Drainage Engrg., ASCE. Vol 122 (2): Allen, R.G., M. Smith, L.S. Pereira and A. Perrier An Update for the Definition of Reference Evapotranspiration. ICID Bulletin. 43(2):1-34. Allen, R.G., W.O. Pruitt, J.A. Businger, L.J. Fritschen, M.E. Jensen and F.H.Quinn Evaporation and transpiration. Chap. 4 in Hydrology Handbook, ASCE Manuals and Reports on Engineering Practice No. 28, ASCE, New York, NY. pp Allen, R.G., L.S. Pereira, D. Raes, and M. Smith Crop Evapotranspiration: Guidelines for computing crop water requirements. Irrigation and Drainage Paper 56, Food and Agriculture Organization of the United Nations, Rome, 300 p. Brunt, D "Notes on Radiation In the Atmosphere:I" Q. J. Roy. Meteor. Soc., 58: Dong, A., Grattan, S.R., Carroll, J.J. and Prashar, C.R.K. (1992). "Estimation of daytime net radiation over well-watered grass." J. Irrig. and Drain. Engrg., ASCE 118(3): Howell, T.A., S.R. Evett, A.D. Schneider, D.A. Dusek and K.S. Copeland Irrigated fescue grass ET compared with calculated reference grass ET. Proceedings of the 4 th National Irrigation Symposium, ASAE, Phoenix, AZ, Nov., Itenfisu, D., R.L. Elliott, R.G. Allen, and I.A. Walter Comparison of reference evapotranspiration calculations across a range of climates. Proceedings of the 4 th National Irrigation Symposium, ASAE, Phoenix, AZ, Nov., Jensen, M.E., R.D. Burman, and R.G. Allen (ed) Evapotranspiration and Irrigation Water Requirements. American Society of Civil Engineers, Engrg Pract. Manual No p. Martin, D.L. and J.Gilley Irrigation Water Requirements, Chapter 2, Part 623, National Engineering Handbook, USDA, Soil Conservation Service. 284 p. Walter, I.A., R.G. Allen, R. Elliott, M.E. Jensen, D. Itenfisu, B. Mecham, T.A. Howell, R. Snyder, P. Brown, S. Echings, T. Spofford, M. Hattendorf, R.H. Cuenca, J.L. Wright, D. Martin ASCE s Standardized Reference Evapotranspiration Equation Proceedings of the 4 th National Irrigation Symposium, ASAE, Phoenix, AZ, Nov., Wright, J.L New Evapotranspiration Crop Coefficients. Journal of Irrigation and Drainage Division, ASCE, 108: Wright, J.L Derivation of Alfalfa and Grass Reference Evapotranspiration. in. Evapotranspiration and Irrigation Scheduling, C.R. Camp, E.J. Sadler, and R.E. Yoder (ed.). Proc. Int. Conf., ASAE, San Antonio, TX. p Wright, J.L., R.G. Allen, and T.A. Howell Conversion between evapotranspiration references and methods. Proceedings of the 4 th National Irrigation Symposium, ASAE, Phoenix, AZ, Nov., 2000.
Figure 1: Schematic of water fluxes and various hydrologic components in the vadose zone (Šimůnek and van Genuchten, 2006).
The evapotranspiration process Evapotranspiration (ET) is the process by which water is transported from the earth surface (i.e., the plant-soil system) to the atmosphere by evaporation (E) from surfaces
More informationComparison of Several Reference Evapotranspiration Methods for Itoshima Peninsula Area, Fukuoka, Japan
Memoirs of the Faculty of Engineering, Kyushu University, Vol. 66, No.1, March 6 Comparison of Several Reference Evapotranspiration Methods for Itoshima Peninsula Area, Fukuoka, Japan by Othoman ALKAEED
More informationIRRIGATION SCHEDULING OF ALFALFA USING EVAPOTRANSPIRATION. Richard L. Snyder and Khaled M. Bali 1 ABSTRACT
IRRIGATION SCHEDULING OF ALFALFA USING EVAPOTRANSPIRATION Richard L. Snyder and Khaled M. Bali 1 ABSTRACT This paper describes the Irrigation Scheduling Alfalfa (ISA) model, which is used to determine
More informationRevised FAO Procedures for Calculating Evapotranspiration Irrigation and Drainage Paper No. 56 with Testing in Idaho 1
Revised FAO rocedures for Calculating Evapotranspiration rrigation and Drainage aper No. 5 with Testing in daho 1 Abstract Richard G. Allen, Martin Smith, Luis S. ereira, Dirk Raes and J.L. Wright n 199,
More informationTHE FAO PENMAN MONTIETH METHOD OF ESTIMATING EVAPOTRANSPIRATION COMPARED WITH NINE OTHER METHODS IN CAPE COAST MUNICIPALITY, GHANA
IJCRR Vol 04 issue 19 Section: Technology Category: Research Received on: 19/07/12 Revised on:04/08/12 Accepted on:25/08/12 THE FAO PENMAN MONTIETH METHOD OF ESTIMATING EVAPOTRANSPIRATION COMPARED WITH
More informationET-BASED IRRIGATION SCHEDULING
Proceedings of the 23rd Annual Central Plains Irrigation Conference, Burlington, CO., February 22-23, 2011 Available from CPIA, 760 N.Thompson, Colby, Kansas ET-BASED IRRIGATION SCHEDULING Allan A. Andales
More informationThe application of climatic data for planning and management of sustainable rainfed and irrigated crop production
Agricultural and Forest Meteorology 103 (2000) 99 108 The application of climatic data for planning and management of sustainable rainfed and irrigated crop production Martin Smith Land and Water Development
More informationA Simulation Model for Evapotranspiration of Applied Water. Morteza N. Orang 1 Richard L. Snyder 2 Shu Geng 3 J. Scott Matyac 4 Sara Sarreshteh 5
A Simulation Model for Evapotranspiration of Applied Water Morteza N. Orang 1 Richard L. Snyder 2 Shu Geng 3 J. Scott Matyac 4 Sara Sarreshteh 5 Abstract The California Department of Water Resources and
More informationAquaCrop theoretical and practical training
AquaCrop theoretical and practical training Day 2 - Climate Johannes Hunink (j.hunink@futurewater.es) Peter Droogers 17-21 Oct-2016, Yerevan, Armenia AquaCrop Conceptual Framework Atmosphere CLIMATE Rain
More informationStatistical Comparison of Reference Evapotranspiration Methods: A Case Study from Srinagar in J&K, India
International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 9 (2017) pp. 3731-3737 Journal homepage: http://www.ijcmas.com Case Study https://doi.org/10.20546/ijcmas.2017.609.460
More informationWater balance in soil
Technische Universität München Water balance Water balance in soil Arno Rein Infiltration = + precipitation P evapotranspiration ET surface runoff Summer course Modeling of Plant Uptake, DTU Wednesday,
More informationCrop Water Requirement. Presented by: Felix Jaria:
Crop Water Requirement Presented by: Felix Jaria: Presentation outline Crop water requirement Irrigation Water requirement Eto Penman Monteith Etcrop Kc factor Ks Factor Total Available water Readily available
More informationCrop Water Requirement using Single and Dual Crop Coefficient Approach
Crop Water Requirement using Single and Dual Crop Coefficient Approach Dr. Falguni Parekh 1 Associate Professor, Water Resources Engineering and Management Institute, Faculty of Technology and Engineering,
More informationSmart Irrigation Controllers: Operation of Evapotranspiration-Based Controllers 1
AE446 Smart Irrigation Controllers: Operation of Evapotranspiration-Based Controllers 1 Michael D. Dukes, Mary L. Shedd, and Stacia L. Davis 2 This article is part of a series on smart irrigation controllers.
More informationComparative study of water requirement with seasonal rainfall for Cereals, pulses and oil seed of Khurda district of Odisha
2018; 6(3): 1377-1381 P-ISSN: 2349 8528 E-ISSN: 2321 4902 IJCS 2018; 6(3): 1377-1381 2018 IJCS Received: 07-03-2018 Accepted: 11-04-2018 Abinash Dalai PhD. Research Scholar, Faculty of SWE, SVCAET & RS,
More informationDevelopment of the Mississippi Irrigation Scheduling Tool-MIST
Development of the Mississippi Irrigation Scheduling Tool-MIST Sassenrath, G.; Schmidt, A.; Schneider, J.; Tagert, M.L.; van Riessen, H.; Corbitt, J.Q.; Rice, B.; Thornton, R.; Prabhu, R.; Pote, J.; Wax,
More informationChanges in crop evapotranspiration and irrigation water requirements
Int. Agrophys., 211, 25, 369-373 INTERNATIONAL Agrophysics www.international-agrophysics.org Changes in crop evapotranspiration and irrigation water requirements C. Paltineanu 1, E. Chitu 2, and E. Mateescu
More informationVariability Analyses of Alfalfa-Reference to Grass- Reference Evapotranspiration Ratios in Growing and Dormant Seasons
University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Biological Systems Engineering: Papers and Publications Biological Systems Engineering 2008 Variability Analyses of Alfalfa-Reference
More informationAnalysis of Evapotranspiration for Pune District
Analysis of Evapotranspiration for Pune District Ranjeet Sabale 1, Aadesh Nimbalkar 2, Mahotsavi Patil 3, Ritu Sagar 4, Prajakta Palaskar 5, 1 Assistant Professor, Civil Engineering Department, Dr. D Y
More informationThe Hydrosphere: Lecture 7: Evapotranspiration. Paul R. Houser,27 March 2012, Page 1
The Hydrosphere: Lecture 7: Evapotranspiration Paul R. Houser,27 March 2012, Page 1 Evapotranspiration evapotranspiration summarizes all processes that return liquid water back into water vapor evaporation
More informationCOMPARISON OF SOME EMPIRICAL EQUATIONS FOR ESTIMATING DAILY REFERENCE EVAPOTRANSPIRATION UDC :631.43:519.6(045)=111
FACTA UNIVERSITATIS Series: Architecture and Civil Engineering Vol. 8, N o 2, 2010, pp. 163-168 DOI: 10.2298/FUACE1002163T COMPARISON OF SOME EMPIRICAL EQUATIONS FOR ESTIMATING DAILY REFERENCE EVAPOTRANSPIRATION
More informationESTIMATION OF EVAPOTRANSPIRATION WITH ANN TECHNIQUE
J. Indian Water Resour. Journal Soc., of Vol. Indian, Water No., Resources January, Society, Vol, No., January, ESTIMATION OF EVAPOTRANSPIRATION WITH ANN TECHNIQUE M. U. Kale, M. B. Nagdeve and S. J. Bagade
More informationWATER PRODUCTION FUNCTIONS FOR CENTRAL PLAINS CROPS
Proceedings of the 24th Annual Central Plains Irrigation Conference, Colby, Kansas, February 21-22, 2012 Available from CPIA, 760 N.Thompson, Colby, Kansas WATER PRODUCTION FUNCTIONS FOR CENTRAL PLAINS
More informationREFERENCE EVAPOTRANSPIRATION: CHOICE OF METHOD
REFERENCE EVAPOTRANSPIRATION: CHOICE OF METHOD F. Sau 1, F.X. López-Cedrón 1 & M.I. Mínguez 2 Universidad de Santiago de Compostela 1 y Universidad Politécnica de Madrid 2 (España) INTRODUCTION During
More informationLecture 5: Transpiration
5-1 GEOG415 Lecture 5: Transpiration Transpiration loss of water from stomatal opening substomatal cavity chloroplasts cuticle epidermis mesophyll cells CO 2 H 2 O guard cell Evaporation + Transpiration
More informationAn evaluation of reference evapotranspiration models in Louisiana
Louisiana State University LSU Digital Commons LSU Master's Theses Graduate School 2004 An evaluation of reference evapotranspiration models in Louisiana Royce Landon Fontenot Louisiana State University
More informationCristian Paltineanu 1, Emil Chitu 2 and Emilia Mateescu 3
TENDINŢE NOI PRIVIND EVAPOTRANSPIRAŢIA ŞI CERINŢELE PENTRU APA DE IRIGARE A UNOR CULTURI HORTICOLE ÎN PRIMUL DECENIU AL SECOLULUI I ÎN SUDUL ROMÂNIEI NEW TRENDS FOR CROP EVAPOTRANSPIRATION AND IRRIGATION
More informationEvaluation of Potential Water Conservation Using Site-Specific Irrigation
Evaluation of Potential Water Conservation Using Site-Specific Irrigation K. C. Stone 1, P. J. Bauer, and J. A. Millen Abstract: With the advent of site-specific variable-rate irrigation (VRI) systems,
More informationThe Science Behind Measuring Depletions
The Science Behind Measuring Depletions 1 The Science Behind Measuring Depletions Salim Bawazir, New Mexico State University Salim Bawazir is Associate Professor in the Civil Engineering (CE) Department
More informationMeasurement of Evapotranspiration Across Different Land Cover Types in the Greater Toronto Area
Measurement of Evapotranspiration Across Different Land Cover Types in the Greater Toronto Area Prepared by: Toronto and Region Conservation and York University 2014 MEASUREMENT OF EVAPOTRANSPIRATION
More informationEvaluating the Best Experimental Method for Estimating Potential Evapotranspiration in Khorasan Razavi, Iran
J. Appl. Environ. Biol. Sci., 4(s)-5, 04 04, TextRoad Publication ISSN: 090-474 Journal of Applied Environmental and Biological Sciences www.textroad.com Evaluating the Best Experimental Method for Estimating
More informationROBUST ESTIMATES OF EVAPOTRANSPIRATION FOR SUGARCANE
ROBUST ESTIMATES OF EVAPOTRANSPIRATION FOR SUGARCANE M G MCGLINCHEY 1 and N G INMAN-BAMBER 1 Swaziland Sugar Association Technical Services, Simunye, Swaziland CSIRO Sustainable Ecosystems, Townsville,
More informationREFERENCE EVAPOTRANSPIRATION ESTIMATION USING CROPWAT MODEL AT LUDHIANA DISTRICT (PUNJAB) A. Patel 1, R. Sharda 2, S. Patel 3 and P.
International Journal of Science, Environment and Technology, Vol. 6, No 1, 2017, 620 629 ISSN 2278-3687 (O) 2277-663X (P) REFERENCE EVAPOTRANSPIRATION ESTIMATION USING CROPWAT MODEL AT LUDHIANA DISTRICT
More informationAsignificant part of precipitation AJES
AJES SIAN JOURNAL OF ENVIRONMENTAL SCIENCE VOLUME 1 ISSUE 1 JUNE, 68-7 e ISSN-976-8947 DOI: 1.7/HAS/AJES/1.1/68-7 Visit us : www.researchjournal.co.in A CASE STUDY Comparison of the values of potential
More informationComparison of Daily and Monthly Results of Three Evapotranspiration Models in Tropical Zone: A Case Study
American Journal of Environmental Sciences 5 (6): 698-705, 2009 ISSN 1553-345X 2009 Science Publications Comparison of Daily and Monthly Results of Three Evapotranspiration Models in Tropical Zone: A Case
More informationOptimizing irrigation requirements for almond trees grown in the South Sinai Governorate
Research Paper Future of Food: Journal on Food, Agriculture and Society 5 (2) Autumn 2017 Optimizing irrigation requirements for almond trees grown in the South Sinai Governorate A. A Farag* 1, M A. A
More informationAGRIMET: MODELING EVAPOTRANSPIRATION FOR IRRIGATION WATER MANAGEMENT
AGRIMET: MODELING EVAPOTRANSPIRATION FOR IRRIGATION WATER MANAGEMENT Peter L. Palmer 1 ABSTRACT In 1983, the U.S. Bureau of Reclamation and Bonneville Power Administration entered into a formal agreement
More informationPeanut Canopy Temperature and NDVI Response to Varying Irrigation Rates
Peanut Canopy Temperature and NDVI Response to Varying Irrigation Rates K. C. Stone, P. J. Bauer, W. J. Busscher, J. A. Millen, D. E. Evans, and E. E. Strickland Abstract: Variable rate irrigation (VRI)
More informationCrop water requirement and availability in the Lower Chenab Canal System in Pakistan
Water Resources Management III 535 Crop water requirement and availability in the Lower Chenab Canal System in Pakistan A. S. Shakir & M. M. Qureshi Department of Civil Engineering, University of Engineering
More informationDRAFT - DO NOT DISSEMINATE
Crop Growth Module: Capturing crop yield response to water deficit within MPMAS Thorsten Arnold tarnold@uni-hohenheim.de Within Ph.D. project Mathematical Programming Multi-Agent System Modeling: An Application
More informationSmart Water Application Technologies (SWAT)
Smart Water Application Technologies (SWAT) Turf and Landscape Irrigation System Smart Controllers CLIMATOLOGICALLY BASED CONTROLLERS 8th Testing Protocol (September 2008) Developed by the SWAT Committee
More informationComparison of field level and regional actual ETc values developed from remote sensing and dual crop coefficient procedure
Comparison of field level and regional actual ETc values developed from remote sensing and dual crop coefficient procedure Daniel J. Howes, Ph.D., P.E. Assistant Professor, Irrigation Training and Research
More informationMANAGEMENT OF CROPS. Thomas Marek Texas A&M University Agricultural Research and Extension Center, 6500 Amarillo Blvd. West, Amarillo, Texas 79106
DETERMINATION OF CROP COEFFICIENTS (K C ) FOR IRRIGATION MANAGEMENT OF CROPS Giovanni Piccinni, Jonghan Ko, Amy Wentz, and Daniel Leskovar Texas A&M University Agricultural Research and Extension Center,
More informationA NEW TECHNIQUE FOR EVALUATION OF CROP COEFFICIENTS:A CASE STUDY
Proceedings of the 2nd IASME / WSEAS International Conference on Water Resources, Hydraulics & Hydrology, Portoroz, Slovenia, May 5-7, 27 7 A NEW TECHNIQUE FOR EVALUATION OF CROP COEFFICIENTS:A CASE STUDY
More informationWater balance at the field and watershed scale.
Water balance at the field and watershed scale. Marco Bittelli Department of Agro-Environmental Science and Technology, University of Bologna, Italy Water Balance Water Balance: computed processes Penman
More informationComparison between various reference evapotranspiration equations for semiarid conditions
Comparison between various reference evapotranspiration equations for semiarid conditions Ramón López-Urrea (1), Francisco Martín de Santa Olalla (), Concepción Fabeiro (), Agueda Moratalla () (1) Instituto
More information2. Crop water requirement 2.1. General
CHAPTER TWO 2. Crop water requirement 2.1. General Crop water requirement may be defined as the quantity of water, regardless of its source, required by crop or diversified pattern of crops in a given
More informationWater Resources Engineering. Prof. R. Srivastava. Department of Water Resources Engineering. Indian Institute of Technology, Kanpur.
Water Resources Engineering Prof. R. Srivastava Department of Water Resources Engineering Indian Institute of Technology, Kanpur Lecture # 13 Today we will continue to discuss some of the abstractions
More informationWater Budget II: Evapotranspiration P = Q + ET + G + ΔS
Water Budget II: Evapotranspiration P = Q + ET + G + ΔS Evaporation Transfer of H 2 O from liquid to vapor phase Diffusive process driven by Saturation (vapor density) gradient ~ (ρ s ρ a ) Aerial resistance
More informationEvapotranspiration Prediction Using Adaptive Neuro-Fuzzy Inference System and Penman FAO 56 Equation for St. Johns, FL, USA
Environmental Engineering 0th International Conference eissn 2029-7092 / eisbn 978-609-476-044-0 Vilnius Gediminas Technical University Lithuania, 27 28 April 207 Article ID: enviro.207.085 http://enviro.vgtu.lt
More informationComparison of Several Methods to Estimate Reference Evapotranspiration
Comparison of Several Methods to Estimate Reference Evapotranspiration 1 2 3 A. R. Zarei *, S. Zare, A. H. Parsamehr 1 Department of Range and watershed management, Faculty of Agricultural science, Fasa
More informationBENCHMARKING METHODOLOGIES FOR WATER FOOTPRINT CALCULATION IN ΑGRICULTURE. 7 Iroon Polytechniou, Zografou, Athens
BENCHMARKING METHODOLOGIES FOR WATER FOOTPRINT CALCULATION IN ΑGRICULTURE ABSTRACT D. Charchousi 1, V.K. Tsoukala 1 and M.P. Papadopoulou 2 1 School of Civil Engineering, National Technical University
More informationSeasonal Curves for Turfgrass Using Dual Coefficient Method
Seasonal Curves for Turfgrass Using Dual Coefficient Method Mark A. Crookston, P.E., D.WRE, CAIS, CIC, CID, CIT, CLIA Northern Water, 220 Water Ave, Berthoud, CO 80513, mcrookston@northernwater.org Abstract
More informationClimate regulating ecosystem services: Introduction to urban microclimates
Climate regulating ecosystem services: Introduction to urban microclimates Dr Gina Cavan April 2012 gina.cavan@manchester.ac.uk Outline Climate regulating ecosystem services Fundamentals of urban climatology
More informationConclusions and future directions
Chapter 4 Conclusions and future directions 4.1 Summary of this work 4.1.1 Canopy-scale model A canopy model combining biochemical and inverse Lagrangian approaches has been presented. Source distributions
More informationA Simple Irrigation Scheduling Approach for Pecan Irrigation in the Lower Rio Grande Valley
ABSTRACT A Simple Irrigation Scheduling Approach for Pecan Irrigation in the Lower Rio Grande Valley Zhorab Samani, Salim Bawazir, Max Bleiweiss, Rhonda Skaggs, John Longworth, Aldo Piñon,Vien Tran Submitted
More informationA SCIENTIFIC APPROACH FOR WATER MANAGEMENT IN RICE FIELDS
Indian J. Soil Cons., 26 (2): 113-116, 1998 A SCIENTIFIC APPROACH FOR WATER MANAGEMENT IN RICE FIELDS A. UPADHYAYA 1 AND S.R. SINGH 21 ABSTRACT Knowledge of onset and withdrawal of effective monsoon as
More informationABSTRACT. KEYWORDS: Reference Evapo transpiration (ETo), Blaney-Criddle Method, Penman-Monteith Method, Irrigation NOMENCLATURE
International Journal of Civil, Structural, Environmental and Infrastructure Engineering Research and Development (IJCSEIERD) ISSN(P): 2249-6866; ISSN(E): 2249-7978 Vol. 4, Issue 1, Feb 2014, 81-88 TJPRC
More informationComparison of the Thornthwaite method and pan data with the standard Penman-Monteith estimates of reference evapotranspiration in China
CLIMATE RESEARCH Vol. 28: 123 132, 2005 Published March 16 Clim Res Comparison of the Thornthwaite method and pan data with the standard Penman-Monteith estimates of reference evapotranspiration in China
More informationAssessment of Hargreaves and Blaney-Criddle Methods to Estimate Reference Evapotranspiration Under Coastal Conditions
American Journal of Science, Engineering and Technology 2018; 3(4): 65-72 http://www.sciencepublishinggroup.com/j/ajset doi: 10.11648/j.ajset.20180304.11 ISSN: 2578-8345 (Print); ISSN: 2578-8353 (Online)
More informationA Computer program for Calculating Crop Water Requirements
Greener Journal of Agricultural Sciences ISSN: 2276-7770; ICV: 6.15 Vol. 3 (2), pp. 150-163, February 2013 Copyright 2017, the copyright of this article is retained by the author(s) http://gjournals.org/gjas
More informationJuly By Charles Swanson, Extension Associate Guy Fipps, Professor and Extension Agricultural Engineer
COLLEGE OF AGRICULTURE AND LIFE SCIENCES TR-354 2009 Evaluation of Smart Irrigation Controllers: Initial Bench Testing Results July 2009 By Charles Swanson, Extension Associate Guy Fipps, Professor and
More informationAdvancing Stormwater Beneficial Uses: ET Mapping in Urban Areas. Ryan Bean 1 and Robert Pitt 2
Advancing Stormwater Beneficial Uses: ET Mapping in Urban Areas Ryan Bean 1 and Robert Pitt 2 1Graduate Student, Department of Civil, Construction, and Environmental Engineering, The University of Alabama,
More informationCrop Water Requirements. Lecture note for Soil and Water Management Course Prepared by Dr ND Nang
Crop Water Requirements Lecture note for Soil and Water Management Course Prepared by Dr ND Nang The crop water need (ET crop) is defined as the amount (or depth) of water needed to meet the water loss
More informationModeling of Environmental Systems
Modeling of Environmental Systems The next portion of this course will examine the balance / flows / cycling of three quantities that are present in ecosystems: Energy Water Nutrients We will look at each
More informationModelling of Crop Reference Evapotranspiration: A Review
All Rights Reserved Euresian Publications 011 eissn 49 056 Available Online at: www.environmentaljournal.org Volume 1, Issue 3: 39-46 Open Access Review Article Modelling of Crop Reference Evapotranspiration:
More informationCrop Yield Predictor for Deficit Irrigation Scheduling ABSTRACT INTRODUCTION
Crop Yield Predictor for Deficit Irrigation Scheduling N. L. Klocke, L. R. Stone, S. Briggeman Norman L. Klocke, Professor, Water Resources Engineering, Kansas State University, 4500 East Mary Street,
More informationIrrigation Rate Calculation for Nursery Crops
Tree Planter's Notes, Volume 41, No. 4 (1990) 22/Tree Planters' Notes Irrigation Rate Calculation for Nursery Crops C. S. Papadopol Research scientist, Ontario Forest Research Institute, Ontario Ministry
More informationAssessment of Evapotranspiration Models under Hyper Arid Environments
Assessment of Evapotranspiration Models under Hyper Arid Environments by Bander Alblewi A Thesis presented to The University of Guelph In partial fulfilment of requirements for the degree of Master of
More informationDATA ANALYTICS FOR OPTIMAL WATER USAGE IN AGRICULTURAL LANDS OF SOUTHERN PARTS OF INDIA
International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 10, October 2018, pp. 668 680, Article ID: IJCIET_09_10_070 Available online at http://www.iaeme.com/ijciet/issues.asp?jtype=ijciet&vtype=9&itype=10
More informationGEOG 402. Forests and Clearings
GEOG 402 Forests and Clearings Microclimate DEFORESTATION What difference does it make when forest is cleared? Forests differ from cleared land in two hydrologically-significant ways. Forests promote:
More informationSensitivity Analysis of FAO-56 Penman-Monteith Method for Different Agro-ecological Regions of India
Environ. Process. (2015) 2:689 704 DOI 10.1007/s40710-015-0107-1 ORIGINAL ARTICLE Sensitivity Analysis of FAO-56 Penman-Monteith Method for Different Agro-ecological Regions of India Subhankar Debnath
More informationLysimeter based crop coefficients for estimation of crop evapotranspiration of black gram (Vigna Mungo L.) in sub-humid region
50 December, 2011 Vol. 4 No.4 Lysimeter based crop coefficients for estimation of crop evapotranspiration of black gram (Vigna Mungo L.) in sub-humid region Pankaj K Pandey 1, Vanita Pandey 2 (1. Department
More informationEstimating water needs of alfalfa and using ET to schedule Irrigation
Estimating water needs of alfalfa and using ET to schedule Irrigation D. Zaccaria, R. Snyder, D. Putnam, A. Montazar, C. Little DWR-Funded Project (2014-2017) aiming at Developing updated information on
More informationDETERMINATION OF CROP CO-EFFICIENT AND CROP WATER REQUIREMENT OF MUNGBEAN ( VIGNA RADITA L. ) IN DL1B AGRO ECOLOGICAL REGION OF SRI LANKA
DETERMINATION OF CROP CO-EFFICIENT AND CROP WATER REQUIREMENT OF MUNGBEAN ( VIGNA RADITA L. ) IN DL1B AGRO ECOLOGICAL REGION OF SRI LANKA K. K. P. Dinushani, CS De Silva, M. D. M. Gunawardhana INTRODUCTION
More informationUSING THE IRRISAT APP TO IMPROVE ON-FARM WATER MANAGEMENT
USING THE IRRISAT APP TO IMPROVE ON-FARM WATER MANAGEMENT John Hornbuckle 1, Janelle Montgomery 2, Jamie Vleeshouwer 3, Robert Hoogers 4 Carlos Ballester 1 1 Centre for Regional and Rural Futures, Deakin
More informationMuch of the material in this class has built up to assess evaporation of landscapes. Here we discuss concepts and data. The field of evaporation has
Much of the material in this class has built up to assess evaporation of landscapes. Here we discuss concepts and data. The field of evaporation has grown and advanced a lot over the past few decades 1
More informationAPPENDIX G. Remote sensing methods to assess the effects of tree thinning on evapotranspiration rates in the Sacramento Mountains
SACRAMENTO MOUNTAINS WATERSHED STUDY APPENDIX G Remote sensing methods to assess the effects of tree thinning on evapotranspiration rates in the Sacramento Mountains This document describes work done by
More information- Fielddata 6. CONSUMPTIVE USE
. CONSUMPTIVE USE.1. INTRODUCTION During the cultivation period following leaching the quantities of irrigation water and the amounts discharged by the drains were measured in connection with the experimental
More informationCLIMATE CHANGE AND THE HYDROTHERMAL AND EVAPOTRANSPIRATION CONDITIONS IN THE PLANNING REGIONS OF BULGARIA
Fourteenth International Water Technology Conference, IWTC 14, Cairo, Egypt 3 CLIMATE CHANGE AND THE HYDROTHERMAL AND EVAPOTRANSPIRATION CONDITIONS IN THE PLANNING REGIONS OF BULGARIA Milena Moteva 1,
More informationESTIMATION OF EVAPOTRANSPIRATION IN SARDAR SAROVAR COMMAND AREA USING WEAP
ESTIMATION OF EVAPOTRANSPIRATION IN SARDAR SAROVAR COMMAND AREA USING WEAP BY : RINA. CHOKSI, GOPAL H. BHATTI AND PROF. H. M. PATEL CIVIL ENGINEERING DEPARTMENT, FACULTY OF TECHNOLOGY AND ENGINEERING,
More informationAgricultural Production Forecasting Using Planning Distribution Model (PDM):A Case Study of the Nam Oon Project
Kasetsart J. (Nat. Sci.) 35 : 344-353 (2001) Agricultural Production Forecasting Using Planning Distribution Model (PDM):A Case Study of the Nam Oon Project Preeyaphorn Kosa and Kobkiat Pongput ABSTRACT
More informationEffluent Nitrogen Management for Agricultural Re-Use Applications
Effluent Nitrogen Management for Agricultural Re-Use Applications Daniel J. Howes 1, Franklin Gaudi 2, Donald Ton 3 Abstract Utilizing treated domestic wastewater to grow forage crops is becoming commonplace
More informationEvaporation. lassoc;ate Professor of Turfgrass Science, Agronomy Depart., Un;v. of Georgia, Experiment (Griffin), GA
IRRIGATION SCHEDULING TECHNOLOGY: THE OLD and NEW Dr. Robert N. Carrow1 Water conservation has become a necessity for many turfgrass managers. Proper irrigation scheduling is a strategy available to all
More informationBAEN 673 / February 18, 2016 Hydrologic Processes
BAEN 673 / February 18, 2016 Hydrologic Processes Assignment: HW#7 Next class lecture in AEPM 104 Today s topics SWAT exercise #2 The SWAT model review paper Hydrologic processes The Hydrologic Processes
More informationTHE OPTIMIZING MODEL OF POTENTIAL EVAPOTRANSPIRATION IN NORTH SYRIA
Ninth International Water Technology Conference, IWTC9 2005, Sharm El-Sheikh, Egypt 41 THE OPTIMIZING MODEL OF POTENTIAL EVAPOTRANSPIRATION IN NORTH SYRIA A.N. Al-Darir * and M. AlDoubiat ** * Professor,
More informationAGRICULTURAL METEOROLOGY IN TURKEY
AGRICULTURAL METEOROLOGY IN TURKEY Dr. Osman ŞİMŞEK TURKISH STATE METEOROLOGICAL SERVICE RESEARCH DEPARTMENT Agricultural Meteorology Division February 2014 AGRICULTURAL METEOROLOGY Studies in Agricultural
More informationYEAR TO YEAR VARIATIONS IN CROP WATER USE FUNCTIONS
Proceedings of the 27th Annual Central Plains Irrigation Conference, Colby, Kansas, February 17-18, 215 Available from CPIA, 76 N.Thompson, Colby, Kansas YEAR TO YEAR VARIATIONS IN CROP WATER USE FUNCTIONS
More informationPlant density, litter and bare soil effects on actual evaporation and transpiration in autumn
Plant density, litter and bare soil effects on actual evaporation and transpiration in autumn S.R. Murphy and G.M. Lodge NSW Agriculture, Tamworth Centre for Crop Improvement, Tamworth NSW. ABSTRACT An
More informationPROGRESS WITH MEASURING AND UTILIZING CROP EVAPOTRANSPIRATION (ETc) IN WALNUT
PROGRESS WITH MEASURING AND UTILIZING CROP EVAPOTRANSPIRATION (ETc) IN WALNUT Allan Fulton, Cayle Little, Richard Snyder, Richard Buchner, Bruce Lampinen, and Sam Metcalf ABSTRACT Since 1982 when the California
More informationMethods of Measuring for Irrigation Scheduling WHEN
AZ1220 Revised 08/14 Methods of Measuring for Irrigation Scheduling WHEN Edward C. Martin Introduction Proper irrigation management requires that growers assess their irrigation needs by taking measurements
More informationIrrigation by Evapotranspiration-Based Irrigation Controllers in Florida
Irrigation by Evapotranspiration-Based Irrigation Controllers in Florida S. L. Davis Agricultural and Biological Engineering Department, University of Florida, P.O. Box 110570, Gainesville, FL 32611-0570;
More informationEvaluation of smart irrigation controllers: Year 2013 results
Evaluation of smart irrigation controllers: Year 2013 results Texas Water Resources Institute TR-469 November 2014 Charles Swanson and Guy Fipps, Ph.D., P.E. Irrigation Technology Program Texas A&M AgriLIfe
More informationBuss, P.; Stevens, S. and Dalton, M. Sentek Pty Ltd, Adelaide, Australia
New Irrigation Scheduling Software combining ETo and soil water dynamics to improve the measurements of daily crop water use, Kc factors and the onset of crop water stress of a flood irrigated alfalfa
More information5.5 Improving Water Use Efficiency of Irrigated Crops in the North China Plain Measurements and Modelling
183 5.5 Improving Water Use Efficiency of Irrigated Crops in the North China Plain Measurements and Modelling H.X. Wang, L. Zhang, W.R. Dawes, C.M. Liu Abstract High crop productivity in the North China
More informationWINTER WASTEWATER LAGOON AND SLURRIES MANAGEMENT
WINTER WASTEWATER LAGOON AND SLURRIES MANAGEMENT H. Neibling 1 1 University of Idaho, Kimberly Research and Extension Center ABSTRACT Proper management of liquid and slurry livestock manure must consider
More informationCrop Water Requirements and Irrigation Scheduling
Irrigation Manual Module 4 Crop Water Requirements and Irrigation Scheduling Developed by Andreas P. SAVVA and Karen FRENKEN Water Resources Development and Management Officers FAO Sub-Regional Office
More informationEstimation irrigation water requirements with derived crop coefficients for upland and paddy crops in ChiaNan Irrigation Association, Taiwan
Agricultural Water Management 82 (2006) 433 451 www.elsevier.com/locate/agwat Estimation irrigation water requirements with derived crop coefficients for upland and paddy crops in ChiaNan Irrigation Association,
More informationCalibrating Net Solar Radiation of FAO56 Penman-Monteith Method to Estimate Reference Evapotranspiration
2013, TextRoad Publication ISSN: 2090-4274 Journal of Applied Environmental and Biological Sciences www.textroad.com Calibrating Net Solar Radiation of FAO56 Penman-Monteith Method to Estimate Reference
More information